The proposed research for this grant period entails a detailed study of the enzymology of glycogen synthesis in bovine heart. The purification of both forms of glycogen synthase, heart protein kinase, and glycogen synthase phosphatase will be of primary importance. Once these enzymes are purified it will be possible to examine the important factors that control glycogen synthase and that regulate the interconversion of this enzyme between the phosphorylated and dephosphorylated forms. Since it is quite possible that the molecular conformation of the glycogen synthase is important in the control of the interconversion reactions as well as its own activity, we will attempt to understand the control of these enzyme reactions in terms of the changes in molecular structure of all of the enzymes involved. There will be a special emphasis on the control of the dephosphorylation reaction that is catalyzed by the heart protein phosphatase. BIBLIOGRAPHIC REFERENCES: C. Nakai and J. A. Thomas, "Effects of Magnesium on the Kinetic Properties of Bovine Heart Glycogen Synthase D." J. Biol. Chem. 250, 4081 (1975). R. L. Mellgren and J. A. Thomas, "Dephosphorylation of Bovine Heart Glycogen Synthase D by E. coli Alkaline Phosphatase," Fed. Proc. 34, 2263 abs. (1975).